Safe knockout arrangement for power press

ABSTRACT

A power press having a knockout bar extending through the slide and carrying a knockout pin which engages the workpiece. Positioned above the slide is a stationary clamp which holds a vertically extending knockout post arranged in the path of movement of the bar. Thus when the slide is raised, the bar strikes the post forcing the bar relatively downwardly to knock the workpiece out of the upper die. The clamp is in the form of a vertically oriented split sleeve with the two halves of the sleeve being biased together for application to the post of predetermined clamping friction at a sufficiently high level to insure reliable knockout of the workpiece while nonetheless providing an impositive connection so that the post, if misadjusted is free to yield endwise upon bottoming of the bar in the slide to prevent damage to the press structure. A manually operated cam is provided for wedging apart the halves of the clamp so as to permit free endwise readjustment of the post in the clamp.

United States Patent [1 1 Wiersma 1 Nov. 12, 1974 SAFE KNOCKOUT ARRANGEMENT FOR POWER PRESS [75] Inventor: Henry R. Wiersma, Palos Heights,

[73] Assignee: Danly Machine Corporation,

Chicago, 111.

[22] Filed: Jan. 24, 1974 [21] Appl. No.: 436,033

[52] 11.8. C1. 72/427, 72/345 [51] Int. Cl ..'B2ld 45/00 [58] Field of Search 29/239; 72/427, 344, 345

[56] References Cited UNITED STATES PATENTS 1,504,771 8/1924 Mallory 72/427 FOREIGN PATENTS OR APPLICATIONS 504,480 7/1951 Belgium 72/345 Primary Examiner lames L. Jones, Jr. Attorney, Agent, or FirmWolfe, Hubbard, Leydig,

Voit & Osaan, Ltd.

[57] ABSTRACT A power press having a knockout bar extending through the slide and carrying a knockout pin which engages the workpiece. Positioned above the slide is a stationary clamp which holds a vertically extending knockout post arranged in the path of movement of the bar. Thus when the slide is raised, the bar strikes the post forcing the bar relatively downwardly to knock the workpiece out of the upper die. The clamp is in the form of a vertically oriented split sleeve with the two halves of the sleeve being biased together for application to the post of predetermined clamping friction at a sufficiently high level to insure reliable ,knockout of the workpiece while nonetheless providing an impositive connection so that the post. if misadjusted is free to yield endwise upon bottoming of the bar in the slide to prevent damage to the press structure. A manually operated cam is provided for wedging apart the halves of the clamp so as to permit free endwise readjustment of the post in the clamp.

6 Claims, 6 Drawing Figures PATENTED HUV 12 1974 SHEET 2 BF 2 w, R m

SAFE KNOCKOUT ARRANGEMENT FOR POWER PRESS It is common in power presses for a workpiece to stick in one of the dies so that means are required for knocking the piece clear when the dies are opened. Where a press has the usual reciprocating upper slide it is known to provide a knockout bar in the slide carrying knockout pins which are in contact with the workpiece and to further provide a relatively stationary knockout post in the path of movement of the bar as the slide moves upwardlyso as to apply a knockout blow automatically in each upward stroke of the slide. Such knockout post must be positionably mounted to vary the impact point in step with the shut height adjustment of the slide for accommodation of dies of different height.

It is, accordingly, an object of the present invention to provide a knockout arrangement which is effective and reliable in developing a predetermined knockout force to insure dislodgement of a workpiece from a die which is nevertheless safe touse, avoiding any possibility of solid bottoming, with possible damage to the press, in the event of inadvertent misadjustment by the press operator. It is a more specific object to provide a knockout arrangement including a clamp having impositive characteristics capable of yielding in the event of a dangerous condition but which is nonetheless capable of developing a predetermined maximum knockout force which is out of the control of the operator and which is adequate for all normal operation.

It is a more specific object to provide a knockout assembly for a power press in which a frictional clamp is provided for the knockout post to grip the latter with predetermined frictional force generated by permanently adjusted biasing springs and in which convenient manual means are provided having a high mechanical advantage for camming or wedging apart the portions of the clamp to throw off the biasing springs thereby to permit free endwise readjustment of the post in the clamp, accomplished both quickly and easily.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a fragmentary diagrammatic elevation showing a portion of a press including press slide and bolster together with dies and workpiece and showing a knockout post and clamping arrangement therefor constructed in accordance with the present invention.

FIG. 2 is a fragmentary elevational view looking along the line 2--2 in FIG. 1.

FIG. 3 is an enlarged front view of the clamp shown in FIG. 1.

FIG. 4 is a side elevation corresponding to FIG. 3.

FIG. 5 is a horizontal section looking along the line 5-5 in FIG. 3.

FIG. 6 is a horizontal section looking along the line 6-6 in FIG. 3.

While the invention has been described in connection with a preferred embodiment, it will be understood that I do not intend to be limited to the particular embodiment shown but intend, on the contrary, to cover the various alternative and equivalent constructions included within the spirit and scope of the appended claims.

Turning to FIGS. 1 and 2 there is shown a portion of a press 10 including a slide 11 and bolster 12. Secured to the slide and bolster, respectively, without an interposed die set, are an upper die 13 and lower die 14 with an interposed workpiece 15. The usual means, not shown but indicated diagrammatically, are provided for vertically reciprocating the slide and for adjusting the position of the slide with respect to the crank which drives it thereby to accommodate dies having different shut height. The figures show the workpiece 15 after it has been acted upon by the dies and in the course of the upward stroke of the slide.

As is conventional in knockout devices, a knockout bar 20 is provided which extends through a horizontal opening 21 in the slide and which has freedom for limited vertical movement. Only one end of the bar 20 is shown in FIGS. 1 and 2 and it will be understood that the structure shown in these two figures may be symmetrically duplicated. Extending downwardly from the knockout bar 20 is a knockout pin 22 which projects directly into engagement with the workpiece 15. The knockout pin is of such length that when the workpiece is engaged and acted upon by the dies, the pin is forced upwardly so that the knockout bar 20 occupies the illustrated upraised position. The knockout bar is guided in its vertical movement by rollers 25. The end 26 of the bar is extended into a projecting position beyond the end of the passage 21.

Arranged in the path of upward movement of the end 26 of the knockout bar is a knockout post 30 which is preferably of circular section having a lower end 31 and a shank 32. The shank is received in a clamp 33 which is welded or otherwise secured to a knockout support bracket 34 which is supported upon a spacer 35 in a stationary position above the reciprocating slide.

In accordance with the present invention the clamp 33 is in the form of a sleeve frictionally engaging the post, the sleeve being vertically split and formed in two halves 41, 42 having alined, or mating, edges. The portion 42 is secured rigidly to the support bracket 34, as by a weld 43, while the portion41 is movable, or floating. For gripping the post, the portion 41 has a vertical groove 45 while the portion 42 has a cooperating groove 46, the grooves being contoured to provide a mating recess or conduit having area contact with the post.

For biasing the two halves of the clamp together so as to exert a predetermined amount of frictional force, a total of eight coiled compression springs are employed, the spring 50 shown in FIG. 5 being taken as representative. The spring is telescoped over a stud 51 which is threaded at 52 into the stationary portion 42 of the clamp and which is threaded at its outer end 53 for receiving a tightly fitted adjusting nut 54 having a washer 55. By using a total of eight such springs 50, four on each side of the centerline, a balanced or uniform force may be applied along an appreciable length of the post. With each spring 50 suitably pre-stressed by its adjusting nut 54, a predetermined frictional force may be developed which is adequate for knocking out any workpiece 15 stuck in the upper die. The means for adjusting the degree of applied force to develop the de sired amount of friction will be discussed in a subsequent paragraph.

In accordance with one of the aspects of the invention manual means are provided for throwing off the springs to relieve the clamping pressure so that the post may be freely readjusted to a different axial position within the clamp. This is accomplished by a manual force transmitting member which is capable of overcoming the force of the springs. Such throw-off is preferably accomplished by providing, on the flat lateral surfaces 61, 62 of the clamp, pairs of opposed cam followers with an interposed, manually movable cam for camming, or wedging, the followers, and thus the halves of the clamp away from one another. Referring to the set of followers which is visible in FIG. 3, the followers, indicated at 63, 64 are in the form of fitted screws carrying rollers 65, 66 bridged by a strap or cover piece 67. Mounted for vertical movement be tween the followers is a cam 70 of tapered or wedge shape. The cam is pivoted at a point 71 to a lever 72 of the second class, which lever is pivoted at its end 73 to member 42. A corresponding set of followers and corresponding cam and lever are provided at the other side of the clamp, in a position of symmetry, with corresponding parts designated by the same reference numerals with addition of subscript a. The front ends of the levers 72, 72a are bridgedby a handle 75 enabling the levers to be thrown simultaneously between an upper position in which the halves of the clamp are pressed together by the springs with a force which is independent of the operator and a lowered position in which the cams are wedgingly interposed between the followers to forcibly separate the two halves of the clamp so that the post is freely slidable in it. After the post has been moved axially to a new position, dependent upon the shut height of the slide, the handle 75 may be swung upwardly to restore the clamping pressure.

It is part of the invention, in one of its aspects, to provide means for establishing a predetermined amount of pre-stress in each of the springs 50 so as to insure a predetermined level of clamping pressure and hence a predetermined amount of friction. This is brought about by telescoping over each of the springs 50 a sleeve 80 which fits under the washer 55 and which has a predetermined length L. The length L is such that when the cam 70 is fully interposed the portion 41 of the clamp bottoms against the sleeve thereby compressing the spring 50 to a degree which corresponds to the length of the sleeve. Thus in originally adjusting the assembly for the desired level of frictional force the cams 70 are interposed between the followers, and the nuts 54 on each of the studs are turned to the point where bottoming of the sleeve 80 occurs upon a temporarily interposed shim to provide a predetermined small degree of clearance, following which the nuts may be considered permanently adjusted for the life of the device.

In a typical operating sequence the post 30 has a downwardly projecting length such that, when the slide is in its uppermost position, engagement of the knockout bar with the lower end of the post causes the knockout bar to be moved downwardly, without, however, exceeding the range of movement of the knockout bar in the slide. in short, the post has an effective length which is short of that which will cause bottoming of the knockout bar in the slide opening 21.

Thus during each cycle a workpiece is deformed by the dies accompanied by upward retreating movement of the pin 22 and bar 20. As the slide approaches the top portion of its stroke, engagement occurs between the post 30 and bar 20, moving the bar downwardly and the pin 22 to its projecting position to dislodge the workpiece which is then removed by suitable unloading elements (not shown) or, if desired, manually.

Should the knockout posts be misadjusted so that it is too short, ejection of the workpiece will not occur, but if the post is adjusted too long the relative stroke of the post with respect to the slide will be excessive, driving the knockout bar 20 down into a bottomed condition within the slide which, in conventional-constructions, is accompanied by the setting up of destructive forces capable of seriously damaging the post and its mount or even the press itself. Using the present clamping construction, however, the frictional force which is developed between the clamp and post, while sufficiently high as to produce a positive and reliable knockout action is, nevertheless, impositive so that once the freedom of movement of the bar 20 in the slide is taken up and bottoming occurs the post harmlessly retreats against the force of friction. The use of a plurality of springs distributed along each of the mating edges on opposite sides of the central recess, makes it possible to distribute the frictional force evenly over a substantial length of the post, thereby avoiding the setting up of concentrated forces which might have the effect of galling the surface of the post when the yielding movement occurs. The endwise force required to produce axial yielding of the post is dependent only upon the initial adjustment, or pre-stress, of the springs outside of the normal control exercised by the operator, thereby insuring a constantly safe condition, even in event of serious error by the press operator during set-up.

Dies donot come in a single standard thickness and thus presses have provision for changing shut height, that is, the height of the slide above the bolster in the lower deadcenter condition. Since adjustment of shut height requires corresponding adjustment in the downwardly projecting length of the post, it is a simple matter, in the present construction, for the operator to pull downwardly upon the handle 75, causing the cams 70, a to be wedged between the cam followers, thereby spreading the halves of the clamp and causing throwoff, or disablement, of the springs. Since only a small amount of spreading movement is required, the taper of the earns 70, 70a may be made quite shallow which, combined with the leverage provided by lever 72, 72a, makes it possible for the operator to compress the stiff springs 50 simultaneously with light manual throw-off force. With the post now sliding free it may be set at any desired projecting length and the handle 75 may be again thrown into its upper or spring-effective position. For convenience the post 30 may be directly calibrated in terms of shut height.

Because of the reliable yield characteristics of the present post-clamping arrangement it is even possible to adjust the post to a shorter length by raising the slide slowly against the end of the post. If this is done, bottoming of the bar 20 at each stroke may be avoided by interposing a shim temporarily between the lower end of the post and the bar during the initial, upward adjusting stroke.

While the invention has been described in terms of smooth frictional engagement between the clamp and post, and while such is preferred, it will be understood that the invention is not limited to smooth surfacing and that shallow multiple detents may be provided between the post and the surfaces which engage the post. Also while it is preferred, in the interest of simplicity, to make the clamp in two halves, it will be understood that the clamp may, if desired, be formed of more than two segments with means for biasing all of the segments together, in which event one or more of the segments, taken together, may constitute a relatively moving half" of the clamp construction. Furthermore, while it is preferred to employ a plurality of stiff compression springs arranged on opposite sides of the cavity and the post which it contains, the term springs as used herein, is a general one and may, indeed, refer to separate sections of the same spring element. The term throw off while applied to the preferred embodiment of the invention in which the springs are compressingly overpowered for separation of the clamping elements is not limited thereto but includes equivalent means for removing the effect of the springs for free slidability of the post. The term support bracket, while referring to supporting element 34 (see FIG. 1) which is in bar form is not intended to be limited to such form and on the contrary shall be interpreted to cover support means broadly. A lever as used herein is any operator capable of crowding action against followers to produce the spreading movement. Finally, the terms cam and camming have to do with means for converting manually applied rocking movement into limited spreading movement with a high degree of mechanical advantage, and thus include the possibility of spreading-type toggle action in which the two portions of the toggle perform the functions of the cam and its followers.

What is claimed is:

1. In a power press the combination comprising a slide, a bolster, cooperating upper and lower dies on the slide and bolster and so constructed that the workpiece tends to cling to the upper die, means for reciprocating the slide relative to the bolster, a knockout bar extending horizontally through the slide and having provision for limited movement therein in the vertical direction, a knockout pin on the knockout bar extending downwardly into engagement with the workpiece and of such length that when the workpiece is deformed by operation of the dies the pin retreats upwardly to move the knockout bar to an upraised position, a support bracket above the slide, a clamp on the support bracket, a vertically extending knockout post in said clamp, said knockout post being arranged in the path of movement of the bar so that when the slide is raised the bar strikes the post forcing the bar relatively downwardly so that the pin thereon engages the workpiece to knock it out of the upper die, the clamp being in the form of a vertically oriented split sleeve having cooperating halves, the clamp having a plurality of springs, means including a throw-off lever coupled to the springs to define an active condition and a throwoff condition, the springs being so connected to the respective halves of the clamp that in the active condition the clamp applies to the post a predetermined clamping pressure which is out of the normal control of the press operator so as to develop a sufficiently high level of friction to insure reliable knockout of the workpiece but nonetheless providing an impositive connection with the post so that in the event of axial misadjustment of the post resulting in bottoming of the bar in the slide the post is free to yield endwise avoiding creation of destructive forces, the lever having provision for movement to the throw-off condition for temporarily and simultaneously disabling the springs accompanied by slight separation of the halves of the clamp thereby to permit free readjustment of the post in the clamp.

2. The combination as claimed in claim 1 in which the throw-off lever has a cam cooperating with opposed cam followers on the respective halves of the clamp so that movement of the cam acts to relatively spread the cam followers.

3. The combination as claimed in claim 1 in which opposed cam followers are provided on the respective halves of the clamp and in which a cam is provided which is of wedge shape, the throw-off lever being pivoted on one of the halves for forcing the cam between the cam followers for spreading apart the halves of the clamp against the force of the springs.

4. The combination as claimed in claim 1 in which the two halves of the clamp are formed of respective blocks of metal having cooperating grooves for accommodating the post and having alined side surfaces, sets of cam followers in opposed relation on the respective side surfaces, wedge shaped cams respectively interposable between the sets of cam followers, a pair of levers extending along the side surfaces for acting upon the respective cams to effect balanced spreading of the clamp, and means for connecting the levers together for simultaneous manual operation.

5. The combination as claimed in claim 1 in which the spring means is in the form of a plurality of coiled compression springs in which studs are provided having adjusting nuts for holding the respective springs and in which the springs are surrounded by respective collars of predetermined length capable of initial bottomed adjustment upon rotation of the respective nuts in the condition of throw-off thereby to insure that the desired degree of pre-stress is developed in each of the springs.

6. In a power press the combination comprising a slide, a bolster, cooperating upper and lower dies on the slide and bolster, means for reciprocating the slide relative to the bolster, a knockout bar extending horizontally through the slide and having provision for limited movement therein in the vertical direction, a knockout pin on the knockout bar extending downwardly into engagement with the workpiece and of such length that when the workpiece is acted upon by the dies the pin retreats upwardly to move the knockout bar to an upraised position, a support bracket above the slide, a clamp on the support bracket, a vertically extending knockout post in said clamp, said knockout post being arranged in the path of movement of the bar so that when the slide is raised the bar strikes the post forcing the bar relatively downwardly so that the pin thereon engages the workpiece to knock it out of the upper die, the clamp being in the form of a vertically oriented split sleeve having cooperating halves with mating edges and defining a central cylindrical cavity for reception of the post, a plurality of compression springs arranged along each of the mating edges on opposite sides of the cavity for biasing the halves together for application to the post of predetermined clamping force which is evenly distributed along a length of the post and which develops a sufficiently high level of friction to insure reliable knockout of the workpiece while nonetheless providing an impositive connection with the post so that in the event of misadjustment of the post resulting in bottoming of the bar in the slide the post is free to yield endwise avoiding creation of destructive forces, and means including a manually operated force transmitting member and cam for camming apart the halves of the clamp so as to permit free readjustmer lt 0E th e post in the clamp. 

1. In a power press the combination comprising a slide, a bolster, cooperating upper and lower dies on the slide and bolster and so constructed that the workpiece tends to cling to the upper die, means for reciprocating the slide relative to the bolster, a knockout bar extending horizontally through the slide and having provision for limited movement therein in the vertical direction, a knockout pin on the knockout bar extending downwardly into engagement with the workpiece and of such length that when the workpiece is deformed by operation of the dies the pin retreats upwardly to move the knockout bar to an upraised position, a support bracket above the slide, a clamp on the support bracket, a vertically extending knockout post in said clamp, said knockout post being arranged in the path of movement of the bar so that when the slide is raised the bar strikes the post forcing the bar relatively downwardly so that the pin thereon engages the workpiece to knock it out of the upper die, the clamp being in the form of a vertically oriented split sleeve having cooperating halves, the clamp having a plurality of springs, means including a throw-off lever coupled to the springs to define an active condition and a throw-off condition, the springs being so connected to the respective halves of the clamp that in the active condition the clamp applies to the post a predetermined clamping pressure which is out of the normal control of the press operator so as to develop a sufficiently high level of friction to insure reliable knockout of the workpiece but nonetheless providing an impositive connection with the post so that in the event of axial misadjustment of the post resulting in bottoming of the bar in the slide the post is free to yield endwise avoiding creation of destructive forces, the lever having provision for movement to the throw-off condition for temporarily and simultaneously disabling the springs accompanied by slight separation of the halves of the clamp thereby to permit free readjustment of the post in the clamp.
 2. The combination as claimed in claim 1 in which the throw-off lever has a cam cooperating with opposed cam followers on the respective halves of the clamp so that movement of the cam acts to relatively spread the cam followers.
 3. The combination as claimed in claim 1 in which opposed cam followers are provided on the respective halves of the clamp and in which a cam is provided which is of wedge shape, the throw-off lever being pivoted on one of the halves for forcing the cam between the cam followers for spreading apart the halves of the clamp against the force of the springs.
 4. The combination as claimed in claim 1 in which the two halves of the clamp are formed of respective blocks of metal having cooperating grooves for accommodating the post and having alined side surfaces, sets of cam followers in opposed relation on the respective side surfaces, wedge shaped cams respectively interposable between the sets of cam followers, a pair of levers extending along the side surfaces for acting upon the respective cams to effect balanced spreading of the clamp, and means for connecting the levers together for simultaneous manual operation.
 5. The combination as claimed in claim 1 in which the spring means is in the form of a plurality of coiled compression springs in which studs are provided having adjusting nuts for holding the respective springs and in which the springs are surrounded by respective collars of predetermined length capable of initial bottomed adjustment upon rotation of the respective nuts in the condition of throw-off thereby to insure that the desired degree of pre-stress is developed in each of the springs.
 6. In a power press the combination comprising a slide, a bolster, cooperating upper and lower dies on the slide and bolster, means for reciprocating the slide relative to the bolster, a knockout bar extending horizontally through the slide and having provision for limited movement therein in the vertical direction, a knockout pin on the knockout bar extending downwardly into engagement with the workpiece and of such length that when the workpiece is acted upon by the dies the pin retreats upwardly to move the knockout bar to an upraised position, a support bracket above the slide, a clamp on the support bracket, a vertically extending knockout post in said clamp, said knockout post being arranged in the path of movement of the bar so that when the slide is raised the bar strikes the post forcing the bar relatively downwardly so that the pin thereon engages the workpiece to knock it out of the upper die, the clamp being in the form of a vertically oriented split sleeve having cooperating halves with mating edges and defining a central cylindrical cavity for reception of the post, a plurality of compression springs arranged along each of the mating edges on opposite sides of the cavity for biasing the halves together for application to the post of predetermined clamping force which is evenly distributed along a length of the post and which develops a sufficiently high level of friction to insure reliable knockout of the workpiece while nonetheless providing an impositive connection with the post so that in the event of misadjustment of the post resulting in bottoming of the bar in the slide the post is free to yield endwise avoiding creation of destructive forces, and means including a manually operated force transmitting member and cam for camming apart the halves of the clamp so as to permit free readjustment of the post in the clamp. 